A sagittal saw blade is a surgical saw with a head that pivots around an axis that is perpendicular to the blade. The United States patent application entitled SURGICAL SAGITTAL SAW WITH INDEXING HEAD AND TOOLLESS BLADE COUPLING ASSEMBLY FOR ACTUATING AN OSCILLATING TIP SAW BLADE AND OSCILLATING TIP SAW BLADE WITH SELF CLEANING HEAD filed 16 Aug. 2006, U.S. Patent Pub. No. US 2007/0119055 A1, the contents of which are incorporated herein by reference, discloses a sagittal saw blade assembly that includes a static blade bar and a blade head. The blade bar is an elongated member that is releasably attached to the handpiece used to actuate the assembly. The blade head is pivotally mounted to the blade bar and has teeth that extend forward from the blade bar. One or more drive links extend from the blade head to the proximal end of the blade bar. The drive links are reciprocated back and forth by a drive assembly internal to the handpiece. The reciprocation of the drive links in turn causes the blade head to pivot back and forth. The pivoting of the blade head is what enables the teeth to cut the tissue against which the blade head is pressed. Generally, this type of blade is known as an oscillating tip saw blade.
An advantage of the oscillating tip saw blade is that the only portion of the blade that pivots is the distally located blade head. In comparison to a conventional sagittal saw blade that pivots from its point of attachment to the complementary handpiece, this blade assembly, when actuated, vibrates less in the hands of the surgeon holding the handpiece. Also, it is common practice to use a cutting guide to properly position a sagittal saw blade relative to the tissue the blade is intended to cut. When a conventional blade is actuated, the oscillating movement of the blade imposes significant wear on the surfaces of the cutting guide defining the slot in which the blade is seated. The blade bar of the oscillating tip blade only minimally moves in this slot. Thus, by using an oscillating tip blade little, if any, of the material forming the cutting guide becomes worn. This reduces the extent to which the surgeon has to flush worn off cutting guide material from the surgical site. Further, use of the oscillating tip blade reduces the extent to which the material forming the guide becomes so worn that the guide itself is rendered useless.
One important component of the above saw blade assembly is the pivot boss. The pivot boss is the cylindrical static member internal to the blade bar against which the blade head both presses and pivots. The outer surface of the blade boss, the surface against which the blade head bears, must be as smooth as possible. This is because surface rough spots will result in wear being concentrated around these points and the complementary surfaces of the blade head that bear against these surfaces. This wear can induce failure in one or both of these components. Even if this wear does not induce structure failure, it can cause an appreciable amount of friction-induced heat to be generated.
The blade bar could be formed by machining a workpiece. In machining, the material forming the workpiece is selectively removed to form the blade bar having the desired geometric features, including the pivot boss. Forming the blade bar using this process can be so expensive that it can be economically impracticable to provide an oscillating tip saw blade.
Furthermore, it is common to form the blade bar of the oscillating tip blade out of opposed upper and lower plates. The blade head and drive rods are sandwiched between the plates. Once these components are assembled together, the opposed plates are secured together to complete the assembly of the oscillating tip blade. Care must be taken in this process to ensure that, post manufacture, the blade bar is as straight as possible. Should the blade bar have any curvature, the blade may bow when pressed against the tissue it is intended to cut. Such curving of the blade can, in turn, result in the blade cutting the tissue along a path that deviates from the intended cut path. This curvature can potentially be so great that it adversely affects the ability of the blade to travel in the slotted cutting guide in which it is inserted.